Multiaxial yield behavior of transversely isotropic closed-cell aluminum foams

Abstract

Mechanical properties of metallic foams will exhibit direction-dependency when the cell shape anisotropy is generated during the manufacturing process. To provide effective design and analysis for the foam-based structures in engineering applications, it is essential to gain a robust understanding of the multiaxial yield properties of anisotropic foams. High-fidelity Voronoi foam model is constructed based on the statistical microstructure information that are measured using micro-CT technique. Transversely isotropic Voronoi foams are generated and adopted to conduct virtual multiaxial experiments. Numerical results show that large plastic deformation is mainly concentrated nearby the rigid platens in uniaxial, biaxial and triaxial compression, while a shear-like deformation localization bands is formed in the compression-shear loading. Sufficient yield points are determined in multiaxial loadings as per a total dissipation energy-based criterion. Numerical isotropic yield surfaces are plotted in the mean-effective stress plane and expand with increasing relative density, which can be well fitted using Zhang yield criteria. For transversely isotropic foams, the dispersion degree of yield points in the mean-effective stress plane is increased with increasing geometric stretch factor. The transversely isotropic yield surfaces are scaled proportionally with the uniaxial yield strength along transverse direction. The extended Hill’s anisotropic yield criterion can generally capture initial yielding behavior of transversely isotropic foams with different anisotropy coefficients and relative densities, outperforming other isotropic yield criteria.